State lawmakers on Thursday narrowly advanced a proposal to ban children under age 12 from playing tackle football in youth leagues, a measure aimed at preventing the brain disease that the family of famed Chicago Bear Dave Duerson blames for his suicide.

Duerson’s son was on hand for an Illinois House committee meeting at the Capitol for the debate over the proposal named for his father. Banning tackling for children is meant to prevent chronic traumatic encephalopathy, a degenerative brain disease that has been linked to repetitive head trauma.

State legislative committee hearings often can be long, monotone debates. On Thursday, though, a former NFL linebacker hit a child-sized mannequin to the hearing room floor in an attempt to demonstrate the danger of concussions, knocking off its Chicago Bears helmet in the process.

“For a youngster at six or seven who’s playing,” former San Francisco 49er Chris Borland said as he hit the mannequin’s helmet with another helmet, “that’s an ugly, violent, nasty concussion that we’re all scared of. You can take some of that out of the game.”

Lawmakers narrowly approved the bill on an 11-9 vote, sending it to the House floor.

Both Democrats and Republicans expressed reservations. Some lawmakers questioned how a ban would be enforced. Others said they withheld support because some groups opposing the proposal weren’t at the hearing and didn’t get to present their side.

In a written statement submitted to lawmakers, Dr. Cynthia LaBella, medical director of the Institute for Sports Medicine at Ann & Robert H. Lurie Children’s Hospital, said the intentions of the bill “are well-meaning.” But she contended “there is no data to show that eliminating tackling in youth football will reduce the risk of neuropsychiatric symptoms or disorders” in children.

On the other side, Dr. Robert Stern, a professor of neurology at Boston University and a CTE researcher, told lawmakers that the disease is caused by “sub-concussions” — small repetitive blows to the head. He said children under 12 are in a period of life that is crucial to brain development.

Stern also said he is confident there will be a sound medical way to test for the disease in a living person within five years, calling it the “critical next step.”

“The problem is we cannot wait for the availability of these tests to begin to examine who may be at greatest risk for CTE as well as for other long-term neurologic problems associated with repetitive brain trauma earlier in life,” Stern said.

CTE disease has been cited as a contributor in the suicides of several former professional football players and has spurred debate over how the sport is played, prompting the NFL to track concussions more closely and put additional safety measures in place.

Tregg Duerson chronicled the life of his father as a man who went from “a full person to a shadow of himself,” struggling with depression, anxiety and personal relationships. The Bears safety took his own life in 2011.

“The action of him taking his own life and donating his brain to science is an action that’s about the future of the game and about safety,” Tregg Duerson said. “What we wanted to get across to lawmakers today is that we have to protect our most precious, important people in this world, and that’s children.”